Wiktionary
n. (context astronomy English) A type of nebula that unlike other types of nebulae does not emit or reflect light and therefore appears as a starless region in the sky.
Wikipedia
A dark nebula or absorption nebula is a type of interstellar cloud that is so dense it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust or material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy.
Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, CO, CS, NH ( ammonia), HCO ( formaldehyde), c-CH ( cyclopropenylidene) and a molecular ion NH ( diazenylium), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding star formation.
The form of such dark clouds is very irregular: they have no clearly defined outer boundaries and sometimes take on convoluted serpentine shapes. The largest dark nebulae are visible to the naked eye, appearing as dark patches against the brighter background of the Milky Way like the Coalsack Nebula and the Great rift. These naked-eye objects are sometimes known as dark cloud constellations and take on a variety of names.
In the inner outer molecular regions of dark nebulae, important events take place, such as the formation of stars and masers.
Dark Nebula is an iOS a skill-based action game developed by 1337 Game Design and released in episodes. Dark Nebula - Episode One was released in August 2009, and Dark Nebula - Episode Two was released in August 2010.
Usage examples of "dark nebula".
Lekket returned his vacant gaze toward the forward viewer, and the dark nebula in the distance.
As we are nowhere near any stars, I originally classified it as a standard dark nebula.
The sky was clear and starry, the ragged mass of the Dark Nebula blotting out the specks of light near the horizon.
He might be now among foothills of brightness or darkness that were hiding behind them the one dark nebula he sought—.
Still the dark nebula with its false halo of blue suns remained apparently as far away as ever.
Space leaped into the screen, star-strewn except where the storm-cloud mass of the dark nebula reared ahead.